feb21 - CS 426 class Mardi Gras...

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CS 426 class Feb 21, 2012 Mardi Gras www.cs.purdue.edu/homes/ssw/cs426/{index.html,syll.pdf,outline} Trusted Operating System security - Read Chapter 5 3. Design - a means to implement the policy - topics like object reuse, audit, logs, intrusion detection Some good design principles for (all) OS (Saltzer+Schroeder): 1. Least privilege - each user/process should have fewest rights possible. 2. Economy of mechanism - protection system should be small, simple, straightforward to permit careful analysis and thorough testing. 3. Open design - the mechanism is public; its security should not depend on ignorance of an attacker. 4. Complete mediation - Check every access attempt. Position the mechanism so that it cannot be circumvented. 5. Permission-based - default is no access. List items to be accessed. 6. Separation of privilege - access should depend on more than one condition, in case one is defeated. 7. Least common mechanism - avoid shared objects, which may be covert channels. 8. Easy to use - If hard to use, users will circumvent it. Security features of ordinary OS: 1. User authentication - userid must be unique; id accurate - password 2. Protect memory - from others and self - RWX - done by hardware paging and segmentation 3. File, I/O device access control - protect from unauth users - done by ACM 4. Allocation and access control to general objects - concurrency and
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